1. Field of the Invention
The present invention relates generally to in-flight entertainment (IFE) systems, and more particularly to IFE systems that provide on a world-wide basis live video/audio programming to passengers/operators of an aircraft using broadcast signals transmitted in either circular or linear polarized form.
2. Description of the Related Art
Conventional IFE systems that distribute live video/audio programming to aircraft passengers, such as an Airborne Satellite Television System (ASTS) manufactured by the assignee of the present invention, derive the live video/audio programming signals from a direct broadcast satellite (DBS) that transmits broadcast signals in the form of right and left circular polarized RF signals. For example, U.S. Pat. No. 5,790,175, issued on Aug. 4, 1998, entitled xe2x80x9cAircraft Satellite Television System for Distributing Television Programming Derived From Direct Broadcast Satellites,xe2x80x9d and U.S. Pat. No. 5,801,751, issued on Sep. 1, 1998, entitled xe2x80x9cDistribution of Satellite Television Programs to Passengers in an Aircraft when it is out of range of the Satellites,xe2x80x9d the disclosures of which are incorporated by reference herein, describe an IFE system that provides live television programming derived from signals broadcast by the DIRECTV DBS system.
Conventional IFE systems, however, are limited because they cannot derive live video/audio programming signals if DBS signals are not in the form of right and left circular polarized RF signals. Although DBS systems that provide service within the continental United States broadcast signals in the form of right and left circular polarized RF signals, DBS systems whose service regions lie outside North and South America generally broadcast signals in the form of horizontal and vertical linear polarized RF signals. For this reason, conventional IFE systems are unable to provide live video/audio programming when the aircraft travels outside the continental United States and into regions serviced by these DBS systems.
An object of the present invention is to provide an IFE system that is capable of deriving video/audio programming signals from satellite broadcast signals transmitted by satellite constellations within any geographical region, so that live video/audio programming may be distributed to aircraft passengers on a worldwide basis.
The IFE system according to the present invention is capable of deriving video/audio programming signals from satellite broadcast signals that are in either circular polarized form or linear polarized form. Consequently, the IFE system of the present invention is capable of receiving live video/audio broadcasts from a variety of DBS service providers around the world, such as STAR CHOICE in Canada, GALAXY Latin America, DIRECTV in the United States, CANAL+in Europe, SHOWTIME in the Middle East, DIRECTV-Japan in Japan, and DIRECPC in the United States, some of which provide satellite broadcast signals in linear polarized form.
More specifically, the IFE system of the present invention consists of an antenna that is disposed on the aircraft and pointed at a satellite or satellite constellation. The antenna is steered based on control signals processed by an antenna controller. The antenna is steered so that it points in the direction of the highest broadcast signal strength that is transmitted by the satellite or satellite constellation. The antenna includes two probes positioned orthogonally relative to one another. The probes extract linear polarized signals received at the antenna and generates signals corresponding to circular polarization by combining the extracted signals in a 90xc2x0 hybrid combiner. The signals are then supplied to an intermediate frequency (IF) signal generating unit. The IF signal generating unit converts the signals into IF signals corresponding to either the received circular or linear polarized waves based on the polarization and frequency band of the satellite broadcast signals, and the global position and attitude of the aircraft.
The IF signals are decoded by a receiver/decoder to provide video/audio signals corresponding to a plurality of service channels. The video signals for the plurality of channels are routed to a video and audio distribution system on the aircraft that distributes live television, internet uplink service, weather service, office network uplink, electronic mail uplink, and other video services to passengers and operators.
The present invention may be implemented with any in-flight distribution video/audio system, whether it is interactive or not. It is equally applicable to systems where video is shown on overhead or bulkhead monitors wherein each passenger views the same program, and to systems where each passenger has a number of available programs.
Another object of the present invention is to provide a method of deriving video/audio programming signals from satellite broadcast signals from satellite constellations within any geographical region, so that live video/audio programming may be distributed to aircraft passengers on a world-wide basis using this method.
Additional objects, features and advantages of the invention will be set forth in the description of preferred embodiments which follows.